U4 switches – Avago Technologies LSI53C120 User Manual
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LSI20101/LSI20102 SCSI Bus Boards
2.4.3 Subsystem Interface Connector J4
A-Side and B-Side SE termination circuitry provides termination for the
SCSI buses. Onboard termination for each of the two physical buses is
controlled in one of two ways: by switches or by the subsystem interface
(J4).
Switches – The LSI20101 board contains the following four switches at
location U4. See
Termination Interface – The termination control on the LSI20101 board
permits the connection of the subsystem harness for external control of
the onboard SCSI terminators.
Connecting the Disable SE-A-TERM or Disable SE-B-TERM pins on J4
to ground turns off the onboard termination for the indicated physical bus.
See
.
Table 3
U4 Switches
Switch
Position
Condition
Description
SW1
ON
Supplied by LSI20101
A-Side
OFF
Not supplied by LSI20101
TERMPWR
SW2
ON
Supplied by LSI20101
B-Side
OFF
Not supplied by LSI20101
TERMPWR
SW3
ON
Disabled
A-Side
OFF
Enabled
Termination
SW4
ON
Disabled
B-Side
OFF
Enabled
Termination